Projection type liquid crystal display unit with reflected incident light

ABSTRACT

A projection type liquid crystal display unit includes (a) a first frame ( 13 ) having a first surface ( 15 ) formed with a first opening ( 13   a ), (b) a second frame ( 12 ) having a second surface formed with a second opening ( 12   a ), and (c) a liquid crystal display panel ( 11 ) sandwiched between the first and second frames ( 13, 12 ) such that an incident light passes through the second opening ( 12   a ), the liquid crystal display panel ( 11 ) and the first opening ( 13   a ) in this order. The first and second frames ( 13, 12 ) are both composed of resin, and the first surface ( 15 ) of the first frame ( 13 ) is roughened.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a projection type liquid crystal display unit,and more particularly to an improvement in a frame supporting a liquidcrystal light bulb therewith for prevention reflection of a lighttherefrom.

2. Description of the Related Art

Recently, various projection type liquid crystal display units such as aliquid crystal projector have been developed. A projection type liquidcrystal display unit is grouped into a light-transmission type and alight-reflection type, and further grouped into a single plate type anda three-plates type in dependence on the number of liquid crystal lightbulbs to be used therein.

Hereinbelow is explained a light-transmission and single plate typeliquid crystal display unit with reference to FIG. 2.

The illustrated liquid crystal display unit is comprised of a lightsource 1, a converging lens 2, a first polarizing plate 3 a, a liquidcrystal light bulb 4, a second polarizing plate 3 b, a projection lens5, and a screen 6.

In operation, a natural light emitted from the light source 1 passesthrough the converging lens 2, and is converted into a linearlypolarized light by the first polarizing plate 3 a. The thus convertedlinearly polarized light enters the liquid crystal light bulb 4, and ismodulated in the liquid crystal light bulb 4 as variation inpolarization in accordance with an image signal. The light leaving theliquid crystal light bulb 4 passes through the second polarizing plate 3b, and is projected onto the screen in an increased size by theprojection lens 5.

Hereinbelow is explained a light-transmission and three-plate typeliquid crystal display unit with reference to FIG. 6.

The illustrated liquid crystal display unit is comprised of a lightsource 1, an optical system 21 for converting a light into a polarizedlight, two dichroic mirrors 22, four all-reflection mirrors 23,converging lenses 24, first polarizing plates 25 a, second polarizingplates 25 b, light liquid crystal bulbs 26, a dichroic prism 27, aprojection lens 28, and a screen 29.

In operation, natural lights emitted from the light source 1 areconverted into linearly polarized lights having the same forwardingdirection and polarizing direction, by the optical system 21. The thusconverted linearly polarized lights are separated into blue, green andred lights by an optical separation system comprised of the two dichroicmirrors 22 and the all-reflection mirrors 23. The blue, green and redlights pass through the associated converging lenses 24 and firstpolarizing plates 25 a, and then, illuminate the associated liquidcrystal light bulbs 26.

The linearly polarized lights entering the liquid crystal light bulbs 26are modulated in the liquid crystal light bulbs 26 as variation inpolarization in accordance with an image signal. The lights leaving theliquid crystal light bulbs 26 enter the associated second polarizingplates 25 b. A portion of the lights displaying black is absorbed intothe second polarizing plates 25 b, whereas a portion of the lightsdisplaying white passes through the second polarizing plates 25 b.

After passing through the second polarizing plates 25 b, optical imagesformed on the liquid crystal light bulbs 26 are combined into a singleoptical image at the dichroic prism 27. The thus produced optical imageis projected onto the screen 29 in an increased size through theprojection lens 28.

Each of the liquid crystal light bulbs 26 is comprised of a liquidcrystal display panel and a frame supporting the liquid crystal displaypanel therewith. The liquid crystal display panel is supported by theframe by being sandwiched between the frame, and is fixed to a body ofthe liquid crystal display unit through the frame.

In the above-mentioned projection type liquid crystal display unit, alight leaving a liquid crystal light bulb sometimes returns back to theliquid crystal light bulb because of reflection, refraction, scattering,diffraction, divergence, deviation in an optical axis and/or aberrationin the parts constituting the liquid crystal display unit, before thelight is projected onto a screen as an image.

If such a light once having left a liquid crystal light bulb andreturned back thereto were reflected or scattered at a surface of aframe of a liquid crystal light bulb, the light would stray into anoptical path having another optical data, resulting in degradation indisplay quality, such as reduction in contrast of a projected image, adouble image or ghost, and/or local non-uniformity in brightness.

In order to avoid the above-mentioned problem, a frame of a liquidcrystal light bulb is usually composed of metal to which a specialcoating is applied.

FIGS. 1A and 1B illustrate cases in which a light is reflected to aframe of a liquid crystal light bulb from other parts constituting theliquid crystal display unit.

A body of a projection type liquid crystal display unit is usuallycoated at an inner wall thereof with black painting, and an optical partis usually coated at a surface thereof with a film which prevents lightreflection.

However, as illustrated in FIG. 1A, a light may be reflected many timebetween a an all-reflection mirror 51 and a converging lens 52, andreach a frame of a liquid crystal light bulb 53. Then, the light isreflected at the frame and subsequently a projection lens 56, and entersa dichroic prism 55. Thus, the light strays into another image data.

As an alternative, as illustrated in FIG. 1B, a light may be wronglyreflected at a dichroic prism 55, and resultingly, reaches a frame of aliquid crystal light bulb 53, if lights emitted from a light source arenot parallel with one another, and/or an optical axis is deviatedbecause of non-uniformity in a gap in a liquid crystal panel.

In addition, a lamp used in a projection type liquid crystal displayunit, such as a halogen lamp, a xenon lamp, a metal halide lamp or ahigh-pressure mercury lamp, and/or light absorption in parts having asmall light-reflection rate generate heat in a body of a liquid crystaldisplay unit, and resultingly, the body is kept at a high temperatureinside. This causes convection current in the body. As a result, a lightis scattered and/or reflected by dusts, and then, reaches a frame. Thelight is further scattered and/or reflected at the frame, resulting inthat the light may enter another image data.

As mentioned above, reflection and/or scattering of a light causedegradation and non-uniformity in projected images.

As mentioned earlier, a liquid crystal light bulb in a projection typeliquid crystal display unit is comprised of a liquid crystal displaypanel and a frame. A module structure of a liquid crystal display unitis grouped into two groups in dependence on whether positioning betweena frame and a liquid crystal display panel is performed based on eithera thin film transistor (TFT) substrate or an opposing substrate of theliquid crystal display panel. This is because that a thin filmtransistor substrate is usually arranged at a side at which a lightleaves, in order to avoid the heat problem. Herein, the positioningbetween a frame and a liquid crystal display panel indicates positioningbetween a reference position defined at a frame or a body of a liquidcrystal display unit and a display area or a center of a display area ofa liquid crystal display panel.

FIG. 10 is an exploded perspective view of a liquid crystal light bulb.

Hereinbelow is explained how a liquid crystal display panel and a frameare positioned to each other, based on a thin film transistor substrateof the liquid crystal display panel, with reference to FIG. 10.

First, as illustrated in FIG. 10(a), a liquid crystal display panel 61is positioned relative to a first frame 62. A flexible printingsubstrate 65 is connected to the liquid crystal display panel 61 forconnecting the liquid crystal display panel 61 to an external circuit(not illustrated).

Then, as illustrated in FIG. 10(b), the liquid crystal display panel 61is adhered to the first frame 62 through an adhesive.

Then, as illustrated in FIG. 10(c), a second frame 63 through which anincident light first passes is fixed to the first frame 62 such that theliquid crystal display panel 61 is sandwiched between the first andsecond frames 62 and 63.

If the first frame 62 were composed of molded resin, the first frame 62would have a surface to which a light is much reflected. Hence, asillustrated in FIG. 10(d), a metal frame 64 is further fixed to thefirst frame 62. In addition, the metal frame 64 is necessary to becoated at a surface thereof with a coating for preventing lightreflection.

Though the first frame 62 may be formed as a metal frame coated at asurface thereof with a coating for light reflection, it would be quitedifficult to manufacture the metal frame with sufficient dimensionalaccuracy, and to position and fix the metal frame to the liquid crystaldisplay panel 61.

The second frame 63 may be composed of molded resin or metal.

FIG. 11 is an exploded perspective view of a liquid crystal light bulb,similarly to FIG. 10.

Hereinbelow is explained how a liquid crystal display panel and a frameare positioned to each other, based on an opposing substrate of theliquid crystal display panel, with reference to FIG. 11.

First, a first frame 72 through which an incident light first passes isfixed to a liquid crystal display panel 71. A flexible printingsubstrate 74 is connected to the liquid crystal display panel 71 forconnecting the liquid crystal display panel 71 to an external circuit(not illustrated).

Then, a second frame 73 is fixed to the first frame 72 such that theliquid crystal display panel 71 is sandwiched between the first andsecond frames 72 and 73.

The second frame 73 may be formed of a metal frame coated at a surfacethereof with a coating for light reflection. However, in order toposition the liquid crystal display panel relative to the first andsecond frames 72 and 73, based on an opposing substrate of the liquidcrystal display panel 71, the opposing substrate would be required tohave high accuracy in an outer shape which is not usually required tohave.

The first frame 72 may be composed of molded resin or metal, but isusually composed of molded resin.

When the metal frame 64 is fixed to the first and second frames 62 and63 both composed of molded resin, there would be caused a problem of anincreased burden in designing a liquid crystal light bulb, due to adifference in a coefficient of linear expansion between the metal frame64 and the first and second frames 62 and 63.

In addition, there are further caused problems of an increase in boththe number of parts and fabrication costs.

Though the above-mentioned problems are explained as problems in alight-transmission type liquid crystal display unit, the same problemsare also caused in a light-reflection type liquid crystal display unit.

Japanese Unexamined Patent Publication No. 4-104244 has suggested aprojection type liquid crystal display unit. The liquid crystal displayunit includes three liquid crystal display panels each of which isilluminated by red, green and blue lights, and synthesizes images formedon the three liquid crystal display panels, to project the synthesizedimages onto a screen. The liquid crystal display unit further includes apolarizing device to which an optical device on which an anti-reflectivefilm is coated is coupled. The polarizing device is adhered to each ofpanel substrates positioned at opposite sides of the three liquidcrystal display panels.

Japanese Unexamined Patent Publication No. 7-64070 has suggested aliquid crystal display device including a first electrode substratehaving pixel electrodes arranged in a matrix and coplanar thin filmtransistors associated with the pixel electrodes, a second electrodesubstrate including an opposing electrode, and a liquid crystal layersealed between the first and second electrode substrates. The liquidcrystal display further includes a polarizing plate adhered to the firstelectrode substrate, and an anti-reflective layer formed on a surface ofthe polarizing plate at which an incident light leaves outwardly.

Japanese Unexamined Patent Publication No. 8-76081 has suggested aprojection type liquid crystal display unit including a liquid crystalpanel having an active matrix substrate on which semiconductor activedevices are formed, an opposing substrate on which an opposing electrodeis formed, and a liquid crystal layer sandwiched between the activematrix substrate and the opposing substrate. In operation, an imageformed on the liquid crystal panel is projected onto a screen through aprojection lens by illuminating the liquid crystal panel from theopposing substrate. The liquid crystal panel is designed to have alight-impermeable pattern for covering the semiconductor active devicetherewith in order to prevent an incident light from reaching directlyto the semiconductor active device. A planar polarizing device isadhered to a surface of the active matrix substrate at which an incidentlight leaves, and is designed to have an anti-reflection layer at asurface at which a light leaves.

Japanese Unexamined Patent Publication No. 11-149071 has suggested aliquid crystal display device including a liquid crystal cell having twosubstrates and a liquid crystal layer sandwiched between the substrates,and a plate located in the vicinity of or making contact with the liquidcrystal cell. The plate has a photoelastic coefficient having acharacteristic relative to a temperature which characteristic is justinverse to the same of a photoelastic coefficient of the substrates. Theplate compensates for non-uniformity in contrast.

However, the above-mentioned problems remain unsolved even in theabove-mentioned Publications.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems in the conventional liquidcrystal display units, it is an object of the present invention toprovide a projection type liquid crystal display unit which is capableof preventing light reflection without an increased burden in designinga liquid crystal display unit and further without an increase in boththe number of parts and fabrication costs.

In one aspect of the present invention, there is provided a projectiontype liquid crystal display unit including (a) a liquid crystal displaypanel, and (b) a frame which supports the liquid crystal display paneltherewith, the frame being composed of resin and having a first surfaceformed with an opening, an incident light passing through the liquidcrystal display panel and then the opening, the first surface beingroughened.

It is preferable that the frame is manufactured by means of a moldhaving a roughened inner surface such that the first surface isroughened in accordance with the roughened inner surface.

For instance, the frame may be composed of polyphenylene sulfide (PPS),polycarbonate (PC), liquid crystal polymer (LCP), polybutyleneterephthalate (PBT), polyether ether ketone (PEEK), or polyether nytril(PEN).

For instance, the first surface may be roughened by sand blasting,plasma etching, etching through the use of chemicals, corona dischargingor radiation of ultra violet having a short wavelength.

It is preferable that an interval between a recess and a projection inthe roughened first surface is equal to or smaller than 100 μm inaverage.

There is further provided a projection type liquid crystal display unitincluding (a) a liquid crystal display panel, and (b) a frame whichsupports the liquid crystal display panel therewith, the frame beingcomposed of resin and having a first surface formed with an openingthrough which the liquid crystal display panel is exposed, an incidentlight being reflected at the liquid crystal display panel being exposedthrough the opening, the first surface being roughened.

There is still further provided a projection type liquid crystal displayunit including (a) a light source, (b) a liquid crystal light bulb whichoptically modulates a light emitted from the light source, in accordancewith an image signal, and (c) a screen onto which a light having beenmodulated by and emitted from the liquid crystal light bulb isprojected, the liquid crystal light bulb including (b1) a liquid crystaldisplay panel, and (b2) a frame which supports the liquid crystaldisplay panel therewith, the frame being composed of resin and having afirst surface formed with an opening, an incident light passing throughthe liquid crystal display panel and then the opening, the first surfacebeing roughened.

There is yet further provided a projection type liquid crystal displayunit including (a) a light source, (b) a liquid crystal light bulb whichoptically modulates a light emitted from the light source, in accordancewith an image signal, and (c) a screen onto which a light having beenmodulated by and emitted from the liquid crystal light bulb isprojected, the liquid crystal light bulb including (b1) a liquid crystaldisplay panel, and (b2) a frame which supports the liquid crystaldisplay panel therewith, the frame being composed of resin and having afirst surface formed with an opening through which the liquid crystaldisplay panel is exposed, an incident light being reflected at theliquid crystal display panel being exposed through the opening, thefirst surface being roughened.

There is still yet further provided a projection type liquid crystaldisplay unit including (a) a light source, (b) a converging lens whichconverges lights emitted from the light source, (c) a first polarizingplate which converts a light having passed the converging lens, into alinearly polarized light, (d) a liquid crystal light bulb whichoptically modulates the linearly polarized light in accordance with animage signal, (e) a second polarizing plate which extracts a lighthaving an intensity varied in accordance with the image signal, out ofthe linearly polarized light leaving the liquid crystal light bulb, (f)a projection lens, and (g) a screen onto which the light leaving thesecond polarizing plate is projected through the projection lens, theliquid crystal light bulb including (d1) a liquid crystal display panel,and (d2) a frame which supports the liquid crystal display paneltherewith, the frame being composed of resin and having a first surfaceformed with an opening, an incident light passing through the liquidcrystal display panel and then the opening, the first surface beingroughened.

There is further provided a projection type liquid crystal display unitincluding (a) a light source, (b) a polarized beam splitter whichseparates S-polarized light out of a light emitted from the lightsource, (c) a liquid crystal light bulb which receives the S-polarizedlight and converts the thus received S-polarized light into a modulatedlight having polarization varying in accordance with an image signal,the modulated light being introduced again into the polarized beamsplitter to extract a light having an intensity varying in accordancewith an image signal, out of the modulated light, (d) a projection lens,and (e) a screen onto which the light leaving the polarized beamsplitter is projected through the projection lens, the liquid crystallight bulb including (c1) a liquid crystal display panel, and (c2) aframe which supports the liquid crystal display panel therewith, theframe being composed of resin and having a first surface formed with anopening through which the liquid crystal display panel is exposed, anincident light being reflected at the liquid crystal display panel beingexposed through the opening, the first surface being roughened.

There is further provided a projection type liquid crystal display unitincluding (a) a first frame having a first surface formed with a firstopening, (b) a second frame having a second surface formed with a secondopening, and (c) a liquid crystal display panel sandwiched between thefirst and second frames such that an incident light passes through thesecond opening, the liquid crystal display panel and the first openingin this order, the first and second frames both being composed of resin,the first surface being roughened.

It is preferable that the first and second frames are composed of thesame resin.

In another aspect of the present invention, there is provided a frameused for supporting a liquid crystal display panel therewith in aprojection type liquid crystal display unit, the frame being composed ofresin and having a first surface formed with an opening, an incidentlight passing through the liquid crystal display panel and then theopening, the first surface being roughened.

It is preferable that the frame is manufactured by means of a moldhaving a roughened inner surface such that the first surface isroughened in accordance with the roughened inner surface.

For instance, the frame is composed of polyphenylene sulfide (PPS),polycarbonate (PC), liquid crystal polymer (LCP), polybutyleneterephthalate (PBT), polyether ether ketone (PEEK), or polyether nytril(PEN).

For instance, the first surface is roughened by sand blasting, plasmaetching, etching through the use of chemicals, corona discharging orradiation of ultra violet having a short wavelength.

There is further provided a frame used for supporting a liquid crystaldisplay panel therewith in a projection type liquid crystal displayunit, the frame being composed of resin and having a first surfaceformed with an opening through which the liquid crystal display panel isexposed, an incident light being reflected at the liquid crystal displaypanel being exposed through the opening, the first surface beingroughened.

There is still further provided a frame used for supporting a liquidcrystal display panel therewith in a projection type liquid crystaldisplay unit, the frame being comprised of a first frame having a firstsurface formed with a first opening, and a second frame having a secondsurface formed with a second opening, the liquid crystal display panelbeing sandwiched between the first and second frames such that anincident light passes through the second opening, the liquid crystaldisplay panel and the first opening in this order, the first and secondframes both being composed of resin, the first surface being roughened.

The advantages obtained by the aforementioned present invention will bedescribed hereinbelow.

The present invention accomplishes a low-reflective characteristic whichcould not be conventionally accomplished in a frame composed of moldedresin. In addition, the present invention makes it no longer necessaryto use a metal frame to which a coating for preventing light reflectionis applied, which was indispensable in a conventional liquid crystaldisplay unit. This ensures reduction in fabrication costs.

Furthermore, since a metal frame is not used in the liquid crystaldisplay unit in accordance with the present invention, the liquidcrystal display unit ensures increased designability and highdimensional accuracy.

In addition, since the frames can be composed of the same resin, itwould be possible to reduce a burden caused by a difference in a linearexpansion coefficient among the frames, in designing a liquid crystaldisplay unit.

The above and other objects and advantageous features of the presentinvention will be made apparent from the following description made withreference to the accompanying drawings, in which like referencecharacters designate the same or similar parts throughout the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate cases in which a light is reflected to aframe of a liquid crystal light bulb from other parts constituting theliquid crystal display unit.

FIG. 2 illustrates a structure of a liquid crystal display unit inaccordance with the first embodiment.

FIG. 3 is an exploded perspective view of a liquid crystal light bulb inthe liquid crystal display unit in accordance with the first embodiment.

FIG. 4 illustrates a unit for measuring an intensity of reflected lightsin a liquid crystal display bulb in the liquid crystal display unit inaccordance with the first embodiment.

FIG. 5 is a graph showing that results of measurement of an intensity ofreflected lights.

FIG. 6 illustrates a structure of a liquid crystal display unit inaccordance with the second embodiment.

FIG. 7 illustrates a structure of a liquid crystal display unit inaccordance with the third embodiment.

FIG. 8 is an enlarged view of a part of the liquid crystal display unitillustrated in FIG. 7.

FIG. 9 illustrates a structure of a liquid crystal display unit inaccordance with the fourth embodiment.

FIG. 10 is an exploded perspective view of a liquid crystal light bulb.

FIG. 11 is an exploded perspective view of a liquid crystal light bulb.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments in accordance with the present invention will beexplained hereinbelow with reference to drawings.

FIG. 2 illustrates a light-transmission and single plate type liquidcrystal display unit in accordance with the first embodiment.

The liquid crystal display unit in accordance with the first embodimentis comprised of a light source 1, a converging lens 2, a firstpolarizing plate 3 a, a liquid crystal light bulb 4, a second polarizingplate 3 b, a projection lens 5, and a screen 6.

In operation, a natural light emitted from the light source 1 passesthrough the converging lens 2, and is converted into a linearlypolarized light by the first polarizing plate 3 a. The thus convertedlinearly polarized light enters the liquid crystal light bulb 4, and ismodulated in the liquid crystal light bulb 4 as variation inpolarization in accordance with an image signal. The light leaving theliquid crystal light bulb 4 passes through the second polarizing plate 3b, and is projected onto the screen in an increased size by theprojection lens 5.

FIG. 3 illustrates a structure of the liquid crystal light bulb 4.

As illustrated in FIG. 3, the liquid crystal light bulb 4 is comprisedof a liquid crystal display panel 11, a first frame 13 having a firstsurface 15 formed with a first opening 13 a, and a second frame 12having a second surface formed with a second opening 12 a. The liquidcrystal display panel 11 is sandwiched between the first and secondframes 13 and 12 such that an incident light 14 passes through thesecond opening 12 a, the liquid crystal display panel 11 and the firstopening 13 a in this order.

A flexible printing substrate 16 is connected to the liquid crystaldisplay panel 11 for connecting the liquid crystal display panel 11 toan external circuit (not illustrated).

The first frame 13 is formed by molding and is composed of resinselected from polyphenylene sulfide (PPS), polycarbonate (PC), liquidcrystal polymer (LCP), polybutylene terephthalate (PBT), polyether etherketone (PEEK), or polyether nytril (PEN).

The first surface 15 of the first frame 13 which extends perpendicularlyto a direction of the light 14 and at which the light 14 leaves theliquid crystal light bulb 4 is roughened by sand blasting. Herein, sandblasting indicates a method of roughened a surface by bombardingabrasive sand at a high speed to an object by virtue of a centrifugalforce or compressed air. In the first embodiment, the first surface 15is roughened by bombarding sand having a diameter of 100 μm or smallerthereto for about 60 seconds.

The first or second frame 13 or 12 may be used for positioning theliquid crystal display panel 11.

The first and second frames 13 and 12 are both composed of resin. Thesecond frame 12 may be composed of resin different from resin of whichthe first frame 13 is composed. However, it is preferable that the firstand second frames 13 and 12 are composed of the same or equivalent resinin order to increase designability and dimensional stability, and reducefabrication costs.

FIG. 4 illustrates a measurement unit for measuring an intensity ofreflected lights in the liquid crystal display bulb 4. The experimentwas conducted to measure the light-reflection characteristic of thefirst surface 15 through the use of the measurement unit illustrated inFIG. 4.

It is assumed that a direction perpendicular to the roughened firstsurface 15, that is, a forwarding direction of the light 14 indicates areference angle or 0 degree, and that a light emitter 17 and a lightreceiver 18 are arranged in a plane perpendicular to the roughened firstsurface 15.

With the light emitter 17 being fixed at an angle of −30 degrees, thelight receiver 18 is made to rotate about a vertical axis indicative of0 degree between 0 degree to 60 degrees. With the light receiver 18being rotated in such a way, an intensity of a light reflected at theroughened first surface 15 is measured.

The measurement was made to the first surface 15 composed of LCP resinand roughened by bombarding sand having a diameter of 100 μm or smallerthereto for about 60 seconds, a surface B composed of LCP resin, but notroughened, and a painted metal surface C.

The results of the measurement are shown in FIG. 5.

The surface B exhibits the highest intensity, and the roughened firstsurface 15 exhibits the lowest intensity.

Though the surfaces B and C have a peak at an angle of 30 degrees, theroughened first surface 15 does not have such a peak. That is, theroughened first surface 15 shows a reflection characteristic which isflat relative to an angle at which the light receiver 18 receives thereflected light.

Herein, there is defined a flatness H as a quotient of I₃₀ divided by I₀(H=I₃₀/I₀) under assumption that an intensity of a light reflected whenthe light receiver 18 is located at an angle of 30 degrees is indicatedby I₃₀, and an intensity of a light reflected when the light receiver 18is located at an angle of 0 degree and 60 degrees is indicated by I₀.

Calculating H in the first surface 15, the surface B and the surface C,the surface B has H of about 25, the surface C has H of about 10, andthe first surface 15 has H of about 5. In practical use, if the firstsurface 15 is roughened by sand blasting such that H of the firstsurface 15 is equal to or smaller than H of the surface C, it would bepossible to have sufficient display performance in the liquid crystaldisplay bulb 4.

Though any interval between a recess and a projection in the roughenedfirst surface 15 may be selected, it is preferable that such an intervalis equal to or smaller than 100 μm in average.

The first surface 15 may be roughened by plasma etching, etching throughthe use of chemicals, corona discharging or radiation of ultra violethaving a short wavelength as well as sand blasting.

As an alternative, the first surface 15 may be formed by means of a moldhaving a roughened inner surface such that the first surface 15 isroughened in accordance with the roughened inner surface. Such aroughened inner surface may be formed by crimping, sand blasting oretching.

As mentioned above, the liquid crystal display unit in accordance withthe first embodiment makes it possible to prevent light reflection byroughening the first surface 15 of the first frame 13.

In addition, the liquid crystal display unit makes it no longernecessary to use a metal frame to which a coating for preventing lightreflection is applied, which was indispensable in a conventional liquidcrystal display unit. This ensures reduction in fabrication costs.

Furthermore, since a metal frame is no longer used in the liquid crystaldisplay unit in accordance with the first embodiment, it is ensured thatboth designability and dimensional accuracy can be increased.

In addition, since the first and second frames 13 and 12 can be composedof the same resin, it would be possible to reduce a burden caused by adifference in a linear expansion coefficient among the frames, indesigning a liquid crystal display unit.

FIG. 6 illustrates a projection type liquid crystal display unit inaccordance with the second embodiment. The liquid crystal display unitis of light-transmission and three-plate type.

The liquid crystal display unit is comprised of a light source 1, anoptical system 21 for converting a light into a polarized light, twodichroic mirrors 22, four all-reflection mirrors 23, converging lenses24, first polarizing plates 25 a, second polarizing plates 25 b, lightliquid crystal bulbs 26, a dichroic prism 27, a projection lens 28, anda screen 29.

In operation, natural lights emitted from the light source 1 areconverted into linearly polarized lights having the same forwardingdirection and polarizing direction, by the optical system 21. The thusconverted linearly polarized lights are separated into blue, green andred lights by an optical separation system comprised of the two dichroicmirrors 22 and the all-reflection mirrors 23. The blue, green and redlights pass through the associated converging lenses 24 and firstpolarizing plates 25 a, and then, illuminate the associated liquidcrystal light bulbs 26.

The linearly polarized lights entering the liquid crystal light bulbs 26are modulated in the liquid crystal light bulbs 26 as variation inpolarization in accordance with an image signal. The lights leaving theliquid crystal light bulbs 26 enter the associated second polarizingplates 25 b. A portion of the lights displaying black is absorbed intothe second polarizing plates 25 b, whereas a portion of the lightsdisplaying white passes through the second polarizing plates 25 b.

After passing through the second polarizing plates 25 b, optical imagesformed on the liquid crystal light bulbs 26 are combined into a singleoptical image at the dichroic prism 27. The thus produced optical imageis projected onto the screen 29 in an increased size through theprojection lens 28.

Each of the liquid crystal light bulbs 26 is designed to have the samestructure as the structure of the liquid crystal light bulb illustratedin FIG. 3.

The liquid crystal display unit in accordance with the second embodimentpresents the same advantages as those presented by the above-mentionedfirst embodiment.

FIG. 7 illustrates a projection type liquid crystal display unit inaccordance with the third embodiment. The liquid crystal display unit isof light-reflection and single plate type.

The liquid crystal display unit is comprised of a light source 1, apolarized beam splitter 31, a liquid crystal light bulb 32, a projectionlens 33, and a screen 34.

The polarized beam splitter 31 separates only S-polarized lights out oflights emitted from the light source 1, and directs the thus separatedS-polarized lights forwardly to the liquid crystal light bulb 32. Adirection of polarization in the S-polarized lights is varied in theliquid crystal panels within a range of 0 to 90 degrees in accordancewith an image signal. Leaving the liquid crystal light bulb 32, theS-polarized lights are transmitted through or interrupted by thepolarized beam splitter 31, and then, projected onto the screen 34 in anincreased size through the projection lens 33.

FIG. 8 is an enlarged view of the liquid crystal light bulb 32.

As illustrated in FIG. 8, the light-reflection type liquid crystal lightbulb 32 is comprised of a liquid crystal display panel 32 a, and a frame32 b which supports the liquid crystal display panel 32 a therewith. Theframe 32 b has a first surface 35 formed with an opening 35 a throughwhich the liquid crystal display panel 32 a is exposed.

An incident light enters the liquid crystal display panel 32 a throughthe opening 35 a, and leaves the liquid crystal display panel 32 athrough the opening 35 a. Hence, in the liquid crystal light bulb 32,the first surface 35 of the frame 32 b is roughened by sand blasting,for instance.

By roughening the first surface 35, the liquid crystal display unit inaccordance with the third embodiment presents the same advantages asthose of the first embodiment.

FIG. 9 illustrates a projection type liquid crystal display unit inaccordance with the fourth embodiment. The liquid crystal display unitis of light-reflection and three-plate type.

The liquid crystal display unit is comprised of a light source 1, twoall-reflection mirrors 41, two dichroic mirrors 42, three polarized beamsplitters 43, three liquid crystal light bulbs 44, a dichroic prism 45,a projection lens 46, and a screen 47.

Each of the liquid crystal light bulbs 44 has the same structure as thatof the liquid crystal light bulb 32 illustrated in FIG. 8.

In operation, natural lights emitted from the light source 1 areseparated into blue, green and red lights by an optical separationsystem comprised of the all-reflection mirrors 41 and the dichroicmirrors 42. The polarized beam splitter 31 separates only S-polarizedlights out of the blue, green and red lights, and directs the thusseparated S-polarized lights forwardly to the liquid crystal light bulb44. A direction of polarization in the S-polarized lights is varied inthe liquid crystal panels within a range of 0 to 90 degrees inaccordance with an image signal.

Leaving the liquid crystal light bulb 44, the S-polarized lights aretransmitted through or interrupted by the polarized beam splitter 43,and then, synthesized into a single light by the dichroic prism 45.Then, an image formed by the light is projected onto the screen 47 in anincreased size through the projection lens 46.

The liquid crystal display unit in accordance with the fourth embodimentpresents the same advantages as those of the first to third embodiments.

While the present invention has been described in connection withcertain preferred embodiments, it is to be understood that the subjectmatter encompassed by way of the present invention is not to be limitedto those specific embodiments. On the contrary, it is intended for thesubject matter of the invention to include all alternatives,modifications and equivalents as can be included within the spirit andscope of the following claims.

The entire disclosure of Japanese Patent Application No. 2000-28394filed on Feb. 4, 2000 including specification, claims, drawings andsummary is incorporated herein by reference in its entirety.

1. A projection type liquid crystal display unit comprising: (a) aliquid crystal display panel; and (b) a frame which supports said liquidcrystal display panel therewith, said frame being composed of resin andhaving a first surface formed with an opening through which said liquidcrystal display panel is exposed, an incident light being reflected atsaid liquid crystal display panel being exposed through said opening,said first surface being roughened.
 2. The projection type liquidcrystal display unit as set forth in claim 1, wherein said frame ismanufactured by means of a mold having a roughened inner surface suchthat said first surface is roughened in accordance with said roughenedinner surface.
 3. The projection type liquid crystal display unit as setforth in claim 1, wherein said frame is composed of a material selectedfrom a group consisting of polyphenylene sulfide (PPS), polycarbonate(PC), liquid crystal polymer (LCP), polybutylene terephthalate (PBT),polyether ether ketone (PEEK), and polyether nytril (PEN).
 4. Theprojection type liquid crystal display unit as set forth in claim 1,wherein said first surface is roughened by sand blasting, plasmaetching, etching through the use of chemicals, corona discharging orradiation of ultra violet having a short wavelength.
 5. The projectiontype liquid crystal display unit as set forth in claim 1, wherein aninterval between a recess and a projection in said roughened firstsurface is equal to or smaller than 100 μm in average.
 6. A projectiontype liquid crystal display unit comprising: (a) a light source; (b) aliquid crystal light bulb which optically modulates a light emitted fromsaid light source, in accordance with an image signal; and (c) a screenonto which a light having been modulated by and emitted from said liquidcrystal light bulb is projected, said liquid crystal light bulbincluding: (b1) a liquid crystal display panel; and (b2) a frame whichsupports said liquid crystal display panel therewith, said frame beingcomposed of resin and having a first surface formed with an openingthrough which said liquid crystal display panel is exposed, an incidentlight being reflected at said liquid crystal display panel being exposedthrough said opening, said first surface being roughened.
 7. Theprojection type liquid crystal display unit as set forth in claim 6,wherein said frame is manufactured by means of a mold having a roughenedinner surface such that said first surface is roughened in accordancewith said roughened inner surface.
 8. The projection type liquid crystaldisplay unit as set forth in claim 6, wherein said frame is composed ofa material selected from a group consisting of polyphenylene sulfide(PPS), polycarbonate (PC), liquid crystal polymer (LCP), polybutyleneterephthalate (PBT), polyether ether ketone (PEEK), and polyether nytril(PEN).
 9. The projection type liquid crystal display unit as set forthin claim 6, wherein said first surface is roughened by sand blasting,plasma etching, etching through the use of chemicals, corona dischargingor radiation of ultra violet having a short wavelength.
 10. Theprojection type liquid crystal display unit as set forth in claim 6,wherein an interval between a recess and a projection in said roughenedfirst surface is equal to or smaller than 100 μm in average.
 11. Aprojection type liquid crystal display unit comprising: (a) a lightsource; (b) a polarized beam splitter which separates S-polarized lightout of a light emitted from said light source; (c) a liquid crystallight bulb which receives said S-polarized light and converts the thusreceived S-polarized light into a modulated light having polarizationvarying in accordance with an image signal, said modulated light beingintroduced again into said polarized beam splitter to extract a lighthaving an intensity varying in accordance with an image signal, out ofsaid modulated light; (d) a projection lens; and (e) a screen onto whichsaid light leaving said polarized beam splitter is projected throughsaid projection lens, said liquid crystal light bulb including: (c1) aliquid crystal display panel; and (c2) a frame which supports saidliquid crystal display panel therewith, said frame being composed ofresin and having a first surface formed with an opening through whichsaid liquid crystal display panel is exposed, an incident light beingreflected at said liquid crystal display panel being exposed throughsaid opening, said first surface being roughened.
 12. The projectiontype liquid crystal display unit as set forth in claim 11, wherein saidframe is manufactured by means of a mold having a roughened innersurface such that said first surface is roughened in accordance withsaid roughened inner surface.
 13. The projection type liquid crystaldisplay unit as set forth in claim 11, wherein said frame is composed ofa material selected from a group consisting of polyphenylene sulfide(PPS), polycarbonate (PC), liquid crystal polymer (LCP), polybutyleneterephthalate (PBT), polyether ether ketone (PEEK), and polyether nytril(PEN).
 14. The projection type liquid crystal display unit as set forthin claim 11, wherein said first surface is roughened by sand blasting,plasma etching, etching through the use of chemicals, corona dischargingor radiation of ultra violet having a short wavelength.
 15. Theprojection type liquid crystal display unit as set forth in claim 11,wherein an interval between a recess and a projection in said roughenedfirst surface is equal to or smaller than 100 μm in average.
 16. Aprojection type liquid crystal display unit comprising: (a) a firstframe having a first surface formed with a first opening; (b) a secondframe having a second surface formed with a second opening; and (c) aliquid crystal display panel sandwiched between said first and secondframes such that an incident light passes through said second opening,said liquid crystal display panel and said first opening in this order,said first and second frames both being composed of resin, said firstsurface being roughened.
 17. The projection type liquid crystal displayunit as set forth in claim 16, wherein said first and second frames arecomposed of the same resin.
 18. The projection type liquid crystaldisplay unit as set forth in claim 17, wherein said frame ismanufactured by means of a mold having a roughened inner surface suchthat said first surface is roughened in accordance with said roughenedinner surface.
 19. The projection type liquid crystal display unit asset forth in claim 16, wherein said frame is composed of a materialselected from a group consisting of polyphenylene sulfide (PPS),polycarbonate (PC), liquid crystal polymer (LCP), polybutyleneterephthalate (PBT), polyether ether ketone (PEEK), and polyether nytril(PEN).
 20. The projection type liquid crystal display unit as set forthin claim 16, wherein said first surface is roughened by sand blasting,plasma etching, etching through the use of chemicals, corona dischargingor radiation of ultra violet having a short wavelength.
 21. Theprojection type liquid crystal display unit as set forth in claim 16,wherein an interval between a recess and a projection in said roughenedfirst surface is equal to or smaller than 100 μm in average.
 22. A frameused for supporting a liquid crystal display panel therewith in aprojection type liquid crystal display unit, said frame being composedof resin and having a first surface formed with an opening, an incidentlight passing through said liquid crystal display panel and then saidopening, said first surface being roughened.
 23. The frame as set forthin claim 22, wherein said frame is manufactured by means of a moldhaving a roughened inner surface such that said first surface isroughened in accordance with said roughened inner surface.
 24. The frameas set forth in claim 22, wherein said frame is composed of a materialselected from a group consisting of polyphenylene sulfide (PPS),polycarbonate (PC), liquid crystal polymer (LCP), polybutyleneterephthalate (PBT), polyether ether ketone (PEEK), and polyether nytril(PEN).
 25. The frame as set forth in claim 22, wherein said firstsurface is roughened by sand blasting, plasma etching, etching throughthe use of chemicals, corona discharging or radiation of ultra violethaving a short wavelength.
 26. The frame as set forth in claim 22,wherein an interval between a recess and a projection in said roughenedfirst surface is equal to or smaller than 100 μm in average.
 27. A frameused for supporting a liquid crystal display panel therewith in aprojection type liquid crystal display unit, said frame being comprisedof a first frame having a first surface formed with a first opening, anda second frame having a second surface formed with a second opening,said liquid crystal display panel being sandwiched between said firstand second frames such that an incident light passes through said secondopening, said liquid crystal display panel and said first opening inthis order, said first and second frames both being composed of resin,said first surface being roughened.
 28. The frame as set forth in claim27, wherein said first and second frames are composed of the same resin.29. The frame as set forth in claim 27, wherein said frame ismanufactured by means of a mold having a roughened inner surface suchthat said first surface is roughened in accordance with said roughenedinner surface.
 30. The frame as set forth in claim 27, wherein saidframe is composed of a material selected from a group consisting ofpolyphenylene sulfide (PPS), polycarbonate (PC), liquid crystal polymer(LCP), polybutylene terephthalate (PBT), polyether ether ketone (PEEK),and polyether nytril (PEN).
 31. The frame as set forth in claim 27,wherein said first surface is roughened by sand blasting, plasmaetching, etching through the use of chemicals, corona discharging orradiation of ultra violet having a short wavelength.
 32. The frame asset forth in claim 27, wherein an interval between a recess and aprojection in said roughened first surface is equal to or smaller than100 μm in average.